Twenty-six years ago, on 17 December 1986, my uncle, Guillermo Cano Isaza, editor of the Colombian daily newspaper, El Espectador, was killed by gunmen paid by Pablo Escobar and his drug trafficking cartel. He had led a journalistic crusade to denounce the corruptive and violent power of drug trafficking. He paid with his life. The newspaper he edited was bombed and became a target as we lived through the bloody years of the so-called "war on drugs".

Back then, and every year since, I've asked myself the same question: was it inevitable? Was there another way to fight the perverse effects of the illegal trade in drugs?

With few positive results to show from the "war", another way now seems possible. Throughout the world, a serious debate is gaining momentum on the inefficacy of prohibition. Prosecuting growers, distributors and consumers leaves a trail of violence and does nothing to curb the sky-high profits of the cartels from corrupting the body politic and police. We need to look at different ways of managing the terrible social effects of drug abuse, while also eliminating the enormous profits of the illegal drug traffic.

It is disappointing, then, to hear that David Cameron has decided to reject the report of a cross-party committee on the UK's drug policy, published last week, which recommended the establishment of a royal commission to review UK drug policies and explore alternatives, such as decriminalisation and legalisation. The prime minister has decided to move in precisely the opposite way from where the world is, and should be, heading.

There was keen expectation that a parliamentary commission in the UK would explore a different approach. Great Britain is one of the main drug-consuming countries in the world. Cameron's decision simply ignores the impact that his country's consumption has on producing countries such as Colombia. Yes, western nations, whose people consume most of the drugs, provide resources, intelligence and military equipment. This makes their politicians feel a little more comfortable about their complicity in the drugs trade. Meanwhile the savage violence that very nearly destroys a country's civil and legal institutions is kept far from their citizens. Votes assured in the UK, the problem kept far away.

That same cynicism is evident in David Cameron's defence of the current policy, "which actually is working in Britain", he says. That policy is not working in the world. Colombia shows concrete advances in, for example, a decrease of 60% in hectares cultivated for coca during the past decade or a similar drop in homicides. But how could anybody go from there to say that the war on drugs "is working"? Consumption keeps growing and other countries – Mexico among them – are now following the same painful path that Colombia went through several years ago.

Today, when many countries both in Latin America and Europe are open to discussing new alternatives – backed by empirical evidence and political resolve – consuming countries such as the UK should be taking the lead. We need a real commitment from these world leaders to stop the disasters of the drugs war. The problems are not abating, they are simply moving through central America as a sequence of "transit countries" (through which the drugs pass en route to the US) experience the same kind of violence and instability that happened in Colombia.

The world is moving. The Global Commission on Drug Policy, led by former presidents Gaviria of Colombia, Zedillo of Mexico and Cardoso of Brazil, as well as Clinton and Carter of the US, has joined the Beckley Foundation in the UK and Colombian and Guatemalan presidents Juan Manuel Santos and Otto Perez Molina, in asking world leaders to support the exploration of more effective options to control the demand and supply of illegal drugs and minimise violence. Where is Great Britain in this debate? Will Cameron let his country be left to one side as major shifts in political and public opinion swirl around his nation? Did he even notice that two US states – Washington and Colorado – voted to legalise marijuana last month? He has a moral responsibility to engage the debate – since we pay the price of his citizens' appetite for drugs.

Precisely 10 years ago this month, a senior British politician said in a debate in the House of Commons: "I ask the Labour government not to return to retribution and war on drugs. That has been tried and we all know that it does not work."